1. Field of the Invention
This invention relates to a method for caulking two members and an apparatus used for the method.
2. Description of the Related Art
Two members can be fixed with one another by a so-called caulking method. For instance, as shown in FIG. 14, the caulking method is carried out to a first member 1a formed with two caulking claws 11a and an engagement recess 10a, and to a second member 2a having an engagement portion 20a that is disposed in the recess 10a. In this state, the caulking claws 11a are bent along the outer surface of the second member 2a to hold the second member 2a. Otherwise, as shown in FIG. 15, the caulking claws 11a are upset inward by flat pushing jigs to hold the second member 2a.
However, in the methods described above, there arise the following problems. That is, when the caulking claws 11a are bent by caulking, as shown in FIG. 16, cracks 99 are liable to occur on the outer surfaces of the caulking claws 11a due to tensile stress that is produced on the outer surface side during the caulking.
When the caulking claws 11a are upset by caulking, cracks do not occur; however, as shown in FIG. 17, central portions of the caulking claws 11a may expand during the upsetting when rigidity of the second member 2a is smaller than that of the first member 1a. In such a case, as shown in FIGS. 18 and 19, the second member 2a can be easily detached from the first member 1a by levering.